Phase-Noise

EQ2440 26/3-2014

Per Zetterberg

I&Q Modulator

tyRe

tyIm

x

x

tfc2coso90

+ tytfj c2expRe

I&Q Demodulator

txtfjty c~2expˆ

tx~ LP tyRe

x

x

tfc2coso90

o90

BP

LP tyIm

With phase-noise

fYfffY 21 LOLOˆ

With noise or interference

fEfYfffY 21 LOLOˆ

Can leak into desired signal, when LO1 is non-ideal.

SDR: Flexibility in digital => lots of E(f)

Time-Domain

tytjtytty expLOˆ

Phase-noise Modulated signal (partially known,

e.g. training)

Phase-noise spectrum:

tF or tF expDon’t be to sure of which is refered to....

PLL

Ref

N

1

PhaseDetector

Loop-filter VCO

Out

- sZs

1

sssZN

ssZNs INOUT /

/)(

Noises:VCO: 1,1/f,1/f^2,1/f^31/N : 1, 1/fPhase detector: 1, 1/fRef input:

Model PLL Dynamics And Phase-Noise Performance

N

1

PhaseDetector

Loop-filter VCO

Phase-Noise Spectrum

ADF4360 (RFX1800) tF exp

,1( ) 10log( )of Hz

T

PL f

P

OFDM

k

ck TN

Ttjkcty

Nfft

2exp

Subcarrier information symbols e.g. QPSK={-

1,+1,-j,+1}

cTTt 0

Cyclic prefix typically

10%Symbol time without CP.

Phase-noise cause inter-carrier interference.

add_phase_noise.m

• Matlab function from MATLAB central.• Spectrum defined in a PSD diagram (dBc) is used as input.•The assumption is used. => Spectrum of is equal to spectrum of . •The real-valued noise is generated in the frequency-domain using FFT (Gaussian noise. Independent from bin to bin).•My question: How accurate is this model ?•My observation: Very neat function.

tjtjtjtj 1expexp 00

tjexp t

t

A Novel Model for Simulation of RF Oscillator Phase Noise

•Paper by Siamak Yousefi potential PhD student at KTH.•Studies problem scetched below.•Some exact mathematical treatment and some approxmiations.•Models noise close to carrier better than Leeson.•Output of integrator unstable (my observation).

Thermal and flicker

noise

Integrator exp(j*a)

For project course.

•Use matlab function add_phase_noise.m.• Provide three basic settings. Good, fair and bad.• Present PLL with slides. Refer to ”Phase Locked Loops for High-Frequency Receivers and Transmitters Part 1-3” and ”Model PLL Dynamics and Phase-Noise Performance”.